1. Field of the Invention
This invention relates to a magnetic recording and reproducing device typical of a video tape recorder.
2. Background Art
The present inventors previously proposed a magnetic recording and reproducing device in which tilted tracks formed by a rotary head are respectively divided into pluralities of areas and wherein signals are recorded in or reproduced from a first train of areas by moving a magnetic tape in a first direction and signals are recorded in or reproduced from a second train of areas by moving the magnetic tape in a second direction opposite to the first direction. Although this is disclosed in Japanese Patent Application No. 148190/84, this application was published on Jan. 17, 1986 and is not believed to qualify as prior art. FIG. 6(A) illustrates such tracks on the magnetic tape. In other words, the tracks are respectively divided into pluralities of areas (6 areas each according to this embodiment). The tracks 1 through 6 are formed on the basis of areas adjacent to each other in the travel direction of the magnetic tape. For instance, data are sequentially recorded in or reproduced from the areas A, B, C on track 1 by moving the magnetic tape in the forward direction. When the record or reproduction of the track 1 is completed the travel direction of the magnetic tape is reversed and then data are recorded or reproduced from the areas A, B, C on track 2.
FIG. 6(B) is a perspective view of a conventional rotary head for indicating the relationship in position on the head between record/reproduce heads 2 and 3 and erase heads 4 and 5. FIG. 5 shows the construction of a conventional rotary head for use in such device. The rotary head shown in FIG. 5 comprises a rotary drum 1 turning clockwise in the drawing. Record/reproduce heads 2 and 3 are attached to the rotary drum 1 at 180 degrees apart. An erase head 4 is used when the magnetic tape is moved in the forward direction and an erase head 5 is used when it is moved in the reverse direction. Both erase heads 4 and 5 are attached to the rotary drum 1.
When data is recorded on track 1, the magnetic tape is moved in the forward direction. Each of the record/reproduce heads 2 and 3 diagonally traces the magnetic tape once until the rotary drum 1 completes a turn. The record/reproduce head 2 is actuated only in the areas A, C and E on track 1 and the record/reproduce head 3 is actuated in the areas B, D and F on track 1, so that data are sequentially recorded in the areas A, B, C, D, E and F on track 1.
On the other hand, the erase head 4, which is twice as wide as the track pitch (P) of the tilted tracks, is attached to the drum 1 in such a manner as to precede the record/reproduce heads 2 and 3 and the erase head 4 simultaneously traces the tracks 1 through 6 of two tilted tracks while the rotary drum 1 turns 6/10 of a revolution. In other words, the rotary drum 1 turns and causes the record/reproduce head 2 to trace the tilted tracks starting with the area A on track 1. The rotary drum 1 further turns and causes the record/reproduce head 3 to trace the tilted tracks starting with the area B on the track 1, whereas the erase head 4 is caused to simultaneously trace the tilted tracks starting with the area A on track 1 and those starting with the area B on the track 1 before the record/reproduce heads 2 and 3 thus trace the tilted tracks. The data stored in the areas A and B are simultaneously erased before any data are recorded therein because the erase head 4 is actuated with track 1 section only. The same operation is repeated thereafter.
On the other hand, when data is recorded on track 2, the magnetic tape is moved in the reverse direction. The rotary drum 1 turns and causes the record/reproduce head 2 to trace the tilted tracks starting with the area G on track 1 and further turns and causes the record/reproduce head 3 to trace the tilted tracks starting with the area F on track 1. The record/reproduce heads 2 and 3 are actuated in the areas A and B on track 2, whereby data are recorded therein. The erase head 5 is caused to simultaneously trace the tilted tracks starting with the area G on track 1 and those starting with the area F on track 1. The data stored in the areas A and B on track 2 are simultaneously erased before any data are recorded therein because the erase head 5 is actuated within the track 2 section only. The same operation is repeated thereafter.
The axial head position of the erase head must be set so that it may always precede the record/reproduce head but the axial head positions in the forward and reverse directions are different when the magnetic tape is moved in the forward and reverse directions to record or reproduce data. Accordingly, two erase heads, i.e., the erase head 4 for use in the forward direction and the erase head 5 for use in the reverse direction must be installed separately as shown in FIGS. 6(A) and 6(B). The disadvantage is that such an arrangement results in the increased number of parts and high production costs.